The Science of Gratitude

New research suggests saying thanks regularly can benefit your health.

A few months ago, I conducted an early Thanksgiving experiment on myself. I was in Reykjavik, Iceland, on a lecture trip. My morning was free, and I took it to write two pages about how lucky I am—something, I’m embarrassed to say, that I had never done before. Here is one thing I wrote: “I’m looking out at a sky that Vikings would have seen. I get to do this—me.” Writing it all down felt very good.

I didn’t know it then, but in making such a list, I was engaging in a scientifically based gratitude intervention, the sort that has been shown, in experimental studies, to make you an all-around happier and more sociable person. Since the year 2000, psychological research has tied gratitude to a host of benefits: the tendency to feel more hopeful and optimistic about one’s own future, better coping mechanisms for dealing with adversity and stress, less instances of depression and addiction, exercising more, and even sleeping better. The degree to which we’re grateful “can explain more variance in life satisfaction than such traits as love, forgiveness, social intelligence, and humor,” sings one recent paper. “Gratitude is strongly related to all aspects of well-being,” declares another.

Given the importance of gratitude to our psychological tool kit, the scientific literature implies that giving thanks once a year isn’t remotely enough. Many of us need to change our deeply ingrained outlooks and behaviors to enjoy these benefits and take the often-dreaded ritual of giving thanks on Thanksgiving more seriously.

“I’m looking out at a sky that Vikings would have seen. I get to do this—me.”

Just how seriously has to do with a new scientific view that gratitude is one of a set of emotions known as “moral affects” that humans developed through evolution. Together with empathy, sympathy, guilt, and shame, they provide a moral compass of actions that we don’t have the time or mental bandwidth to think deeply about. These instinctive feelings impel vital behaviors that help us survive (or did in our evolutionary past, in any case).

In the case of gratitude, scientists consider that the desired behavior is forming bonds of trust with others. We naturally help our relatives because what’s good for them helps promote the genes that we share with them. But why should we ever help out a non-relative? We might expend valuable resources and get nothing back. That’s a key problem in evolutionary theory. Yet researchers agree that there’s a benefit to being part of a wider, cooperative community that can protect you in difficult times.

The catch is that the benefit kicks in only if everybody is as cooperative as you are. But how do you know they will be? There are plenty of reasons to fear being used or exploited. But if it’s possible to suppress distrust and make it feel good to help out those who are not our kin it would help bind us to larger groups. Gratitude does that by being “both a response to moral behavior and a motivator of moral behavior,” as one study puts it. Being part of a bigger group means that grateful people have more places to turn for help and support when they need it.

If this evolutionary account is right, then gratitude should show up in other animals, too. The primatologist Frans de Waal observed what looks like gratitude in chimpanzees; they tend to share their food with individuals who have recently groomed them—the ones to whom, we presume, they feel grateful.

The catch is that the benefit kicks in only if everybody is as cooperative as you are.

So perhaps we ought to be thanking Darwin around the dinner table this Thanksgiving. Gratitude studies seem to be furnishing the latest evidence that moral goodness starts from the systems we developed as caring and empathetic social primates.

Martin Nowak, the director of Harvard’s Program for Evolutionary Dynamics, outlined the drivers that explain cooperation’s central role in human behavior in his recent book Super Cooperators. Starting with the basic model of reciprocity such as “I scratch your back if you scratch mine,” he argues that in evolution unilateral scratching can bring benefits to the whole group and confer a special advantage on the scratcher. Nowak packages these ideas of cooperation under the heading of “snuggle for survival.”

It’s an apt metaphor. The further the research in evolutionary psychology goes, the more cooperation—not competition—is emerging as the defining human trait. Gratitude is a sign of moral behavior and a motivator of others to behave morally towards us. Saying thanks often and loudly enough for others to hear thus translates into tangible rewards.

Chris Mooney is a science and political journalist, podcaster, experienced trainer of scientists in the art of communication, and the host of Climate Desk Live. He is the author of four books, including the New York Times bestselling The Republican War on Science.